Tube forming apparatus



Maw}! 1943. s. R. GIEIST, sR., El AL TUBE FORMING APPARATUS Filed April 14, 1945 Fig. 1

IN V EN TOR.

Sidney R. Geist Sn AND Norman R- Dal/LS My Fig. 2

ATTORNEY Patented Mar. so, 1948' 4 UNITED STATES PATENT. OFFICE 'rnnr: roimmo ma aarus r Sidney B. Geist, Sr., New York, and Norman R.

Davis, Elmhnrst Long Island, N. Y., assignors to Gemloid Corporation, Eimhnrst, Long Island, N. Y., a corporation of New York Application April 14, 1945, Serial No.588320 Our invention relates to a novel apparatus for. sealing plastic sheeting, and more particularly our invention relates to a novel apparatus adapted to seal the opposed edges of a thermoplastic sheet together to form a tube by applying an internal heat thereto by means of radio frequency current.

In the manufacture of tubes from plastic sheeting it has been customary to join the edges of the sheeting by applying a solvent adapted to soften ,or partially dissolve the surfaces of the contacting opposed edges of the plastic sheeting so that by means of heat and pressure the softened edges will coalesce to form a bond. Alternatively, an'adhesive has been employed and the adhesive either contains a solvent that is activated by heat or the adhesive itself is activated' or set by means of heat. Where the plastic-sheeting is thermoplasti in nature, then heat may be directly applied to soften the plastic sheet edges to weld them together.

In each of these instances the heat must be applied in sufficient amounts to penetrate through the relatively poorly conducting plastic sheeting so as to raise the contacting surfaces of a plastic sheet to a. temperature that will soften said surfaces or activate the adhesive thereon. The quantity of heat applied, therefore, may deleteriously affect the outer portions of the plastic sheet which must be carried to a relatively higher temperature to obtain the required heat at the interface area.

These deleterious effects of overheating can be avoided by the use of radio frequency heating by means of which heat is set up internally in the plastic positioned between two high frequency anodes. The types of apparatus hitherto suggested for welding plastic sheetings by radio frequency current have been unsatisfactory since they do not properly efiiciently position the plastic sheeting for welding nor do they apply pressure. in the most effective manner.

The apparatus of our invention provides an efficient manufacturing means for positioning the edges of sheeting, and particularly the two edges of a sheet so as to form that sheet into a tube and for applying welding pressure thereto.

The object of the present invention, therefore,

is to provide an apparatus for efficiently welding plastic sheet material.

It is a further object of the present invention to provide an apparatus adapted to hold plastic sheeting in tube form while sealing the edges of the sheeting by radio frequency current.

It is a further object of the present invention to provide an apparatus by means of which plastic 1: Claims. (01. 154-42) 4 sheeting can be arranged on a rack prior to its insertion between the actual heating electrodes to facilitate the welding operation.

Otherobiects of the invention willbe apparent from a, consideration of the specific description which follows.

The various objects are accomplished by providing a rack for pie-positioning the plastic sheeting in a ram pressing, radio frequency current heating seam welding device. v

Fig. 1 is a front view of the apparatus of our invention.

Fig. 2 is an Fig. 1.

Fig. 3 is a perspective view of the rack adapted to hold the plastic sheeting in tube form.

Fig. 4 is a perspective view of an element around which the sheeting is wound into tube form for insertion in the rack.

Referring now more specifically to the drawings, in Fig. 1 we show a piston l0 operated from a hydraulic cylinder ll. mounted on a cross piece i2 supported by two vertical elements l3 and It. To the piston I0 is secured the cross piece l6 which moves vertically and is guided by the vertical elements i3 and i4. Secured to the cross piece I6 is an insulating element I1 on which is placed and secured the electrode [8 suitably conend view, taken along line 2--2 of nected as shown by the conductor l9 to a source 1 tube retaining side bars 24 and 25 hingedly connected at 26, 21, 28, and 29- to the base frame. At the opposite ends of the rack 22 are recesses 30 and 3| into which recesses fit the ends of center piece 32 of the element 33 which comprises a center piece 32 with two side elements 34 and 35 secured thereto. i

As shown in Figures 2 and 4, a plastic sheet 36 is arranged or wrapped around the element 33 and its side elements 34 and 35 with the edges 51 and 58 overlapping and resting on the center piece 32. with the sheet 36 wrapped about the element 33, the element 33 is placed in the rack 22, the ends of the centerpiece 32 fitting into the recesses 30 and 3t of the rack 22.

The side bars 24 and 25 are shown brought down so as to uniformly press, as shown in Fig, 2, against the plastic sheeting 38 so as to maintain it in proper position for the welding operation. The

silient supporting elements 31 and 33 yield under the pressure and the rack 22 moves downwardly until the springs 3'! and 33 are compressed. Radio high frequency current is introduced through conductor i9 between the upper electrode l3 and the lower electrode 32 which is grounded through 4|.

Heat is thereupon developed between the overlapped edges 51 and 58 which causes the thermoplastic sheet material to soften and coalesce forming a secure bond between the overlapped edges 51 and 53.

When the operation is completed the piston I3 4 rack with said cooperating rack element under said pressure element, said means comprising tracks adapted to receive said rack.

, 3. Means for heat sealing plastic material comprising a pressure element, an electrode mounted on said pressure element, means for applying high frequency current to said electrode, means for insulating said electrode, means for applying pressure to said pressure element, in combination with a rack and a cooperating rack element, said rack element being shaped to receive plastic material wrapped thereabout and having portions extending beyond the ends of the wrapped plastic material adapted to be received by said rack, means mounted on said rack forholding plastic material 7 in wrapped position, means for positioning. said is retracted carrying up with it the attached electrode IS, the rack 22 is withdrawn from the tracks 20 and 2|, and the side bars 24 and 25 lifted up and the welded plastic tube slipped ed the element 33.

Thus, the plastic sheeting 36 is preshaped to tube form over the element 33, secured in position in the rack 22, and such racks with sheeting in position may be continuously fed into the welding device for the heating and pressing operation that efiects the edge welding.

The operation of the apparatus is essentially simple and the assembly of the tube in and on the rack is such as to make tube forming operation rapid and emcient. The lower electrode 32 which is the center piece of the rack element 33 is preferably grounded through the frame via the tree 20 and 2 i It is to be understood that various modifications of this invention will suggest themselves to those skilled in the art from a consideration of the specific description and showing here given. It is to be understood that the various details of the various forms of our invention can be modified and we intend to be limited only by the claims appended hereto.

We claim: 7

1. Means for heat sealing plastic material comprising a pressure element, an electrode mounted on said pressure element, means for applying high frequency current to said electrode, means for insulating said electrode, means for applying pressure to said pressure element, in combination with a rack and a cooperating rack element, said rack element being shaped to receive plastic material wrapped thereabout and having portions extending beyond the ends of the wrapped plastic material adapted to be received by said rack, means mounted on said rack for holding plastic material in wrapped position, means for positioning said rack with said cooperating rack element under said pressure element.

2. Means for heat sealing plastic material comprising a pressure element, an electrode mounted on said pressure element, means for applying high frequency current to said electrode, means for insulating said electrode, means for applying pressure to said pressure element, in combination with' rack with said cooperating rack element under said pressure element, said means comprising tracks adapted to receive said rack, and means for yieldably holding said rack in said tracks.

4. Means for heat sealing plastic material com prising a pressure element, an electrode mounted on said pressure element, means for applying high frequency current to said electrode. means for insulating said electrode, means for applying pressure to said pressure element, in combination with a rack and a cooperating rack element, said rack element being shaped to receive plastic material wrapped thereabout and having portions extending beyond the ends of the wrapped plastic material adapted to be received by said rack, means mounted on said rack for holding said plastic material in wrapped position, said means comprising side bars hingedly mounted on said rack, means for positioning said rack with said cooperating rack element under said pressure element.

5. Means for heat sealing plastic material comprising a pressure element, an electrode mounted on said pressure element, means for applying high frequency current to said electrode, means for insulating said electrode, means for applying pressure to said pressure element, in combination with a rack and a cooperative rack element, said rack element comprising a center piece and two attached side elements, said rack element being shaped to receive plastic material wrapped thereabout and having portions extending beyond the ends of the wrapped plastic material adapted to be received by said rack, means mounted on said rack for holding Said plastic material in wrapped position, said means comprising side bars hingedly mounted on said rack, means for positioning said rack with said cooperating rack element under said pressure element.

6. Means for heat sealing plastic material comprising a pressure element, an electrode mounted on said pressure element, means for applying high sure to said pressure element, in combination with a rack and a cooperating rack element, said rackelement comprising a center piece and two attached side elements, said rack element being shaped to receive plastic material wrapped thereabout and having portions extending beyond the ends of the wrapped plastic material adapted to be received by said rack, means mounted on said rack for holding said plastic material in wrapped position, said means comprising side bars hingedly mounted on said rack, means for positioning said rack with said cooperating rack element under said pressure element and means for grounding said center piece.

7. A high frequency sealing apparatus for iorming tubing from thermoplastic sheeting thereabout, said rack adapted to surround and hold the said rack elementhaving the wrapped plastic sheeting thereabout without distorting said wrapped sheeting, means comprising side bars hingedly mounted on said rack for holding said plastic sheeting in position with overlapping edges, 8. A high frequency sealing apparatus for ,forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element, said 'rack element comprising a center piece and two side bars fixed in spaced relation to said center piece, said rack element being shaped to receive plastic sheeting wrapped in tube form thereabout, said rack adapted to surround and hold the said rack element having the wrapped plastic sheeting thereabout without distorting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said plastic sheeting in position with overlapping edges and means for applyinghigh frequency current to said'overlapped plastic sheet edges. 7

9. A high frequency sealing apparatus for forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element, said rack element comprising a center piece and two side bars fixed in spaced relation to said center piece, said' rack element being shaped to receive plastic sheeting wrapped in tube torm thereabout, said rack adapted to surround and hold the said rack element having the wrapped plastic sheeting thereabout without distorting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said, plastic sheeting in position with overlapping edges and means forvapplying high Irequency current and pressure to said overlapped plastic sheet edges.

10. A high frequency sealing apparatus for forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element. said rack element comprising a center piece and two side bars fixed in spaced relation to said center piece, said. rack element being shaped to receive plastic sheeting wrapped in tube form thereabout and having portions extendin beyond the ends or the wrapped plastic sheetin adapted to be received by said rack, said rack adapted to surround and hold the said rack element having the wrapped plastic sheeting thereabout without distorting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said plastic sheeting inposition with overlapping edges and means for applying high frequency current and pressure to said overlapped plastic sheet edges.

11. A high frequency sealing apparatus for forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element, said rack element comprising a center piece and two side bars fixed in spaced relation to said center piece, said rack element being shaped to receiveplastic sheeting wrapped in tube iorm thereabout. said rack adapted to surtorting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said plastic sheeting in position with overlapping edges and means for applying high frequency current and pressure to said overlapped plastic sheet edges and means for yieldably positioning said rack and rack element so that the overlapped edges of the plastic sheeting are between the center piece of the rack element and the means for applying -high frequency current and pressure.

12. A high frequency sealing apparatus for forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element, said rack element comprising a center piece and two side pars fixed in spaced relation to said center piece, said rack element being shaped to. receive plastic sheeting wrapp d in tube form thereabout, said rack adapted to surround and hold the said rack element having the wrapped plastic sheeting thereabout without dis-- torting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said plastic sheeting in position with overlapping edges and means for applying high frequency current and pressure to said overlapped plastic sheet edges, said means comprising an electrode adapted to be pressed against said overlapped edges.

13. A high frequency sealing apparatus for forming tubing from thermoplastic sheeting which comprises a rack and a cooperating rack element, said rack element comprising a center piece and two side bars fixed in spaced relation to said center piece, said rack element being shaped to receive plastic sheeting wrapped in tube form thereabout, said rack adapted to surround and hold the said rack element having the wrapped plastic sheeting thereabout without distorting said wrapped sheeting means comprising side bars hingedly mounted on said rack for holding said plastic sheeting, in position with overlapping edges and means for applying h frequency current and pressure to said overlapped plastic sheet edges, said means comprising an electrode adapted to be pressed against said overlapped edges and means for grounding the centerpiece of said rack element.

- I SIDNEY R. GEIST, SR.

NORMAN R. DAVIS.

REFERENCES CITED The following references are or record in the vfile or this patent:

UNITED STATES PATENTS Germany Apr. 22, 1938 

